This application is the US national phase of international application PCT/IT00/00346 filed Aug. 23, 2000, which designated the US.
The present invention relates to stable, non-hygroscopic salts of L-carnitine and lower alkanoyl L-carnitine endowed with enhanced nutritional and/or therapeutical efficacy with respect to their inner salts congeners and to solid compositions containing such salts, particularly suited to oral administration.
It has long since known that carnitine and its alkanoyl derivatives lend themselves to various therapeutical utilizations such as e.g. in the cardiovascular field for the treatment of acute and chronic myocardial ischaemia, angina pectoris, heart failure and cardiac arrhythmias. Acetyl L-carnitine is used in the neurologic field for the treatment of both central nervous system disturbances and peripheral neuropathies, particularly diabetic peripheral neuropathy. Propionyl L-carnitine is used for the treatment of chronic arteriosclerosis obliterans, particularly in patients showing the symptom of severely disabling intermittent claudication.
On the other hand, a widespread promotion of carnitine and derivatives thereof has rapidly been taking place towards utilizations other than those purely therapeutical, ever though allied to them.
It has, in fact, been widely recognized that in professional athletes as well as in any subject practising sport at amateur level, L-carnitine supplies energy to the skeletal musculature and increases the resistance to prolonged, intense stress, enhancing the performance capability of such individuals.
In addition, L(xe2x88x92)-carnitine or its lower alkanoyl derivatives constitute indispensable nutritional supplements for both vegetarians, whose diets have a low carnitine content as well as a low content of the two amino acids, lysine and methionine (the precursors of the biosynthesis of L(xe2x88x92)-carnitine in the kidneys and liver) and those subjects who have to live on a diet poor in protein for prolonged periods of time.
Consequently, various compositions containing carnitine or derivatives thereof, either as single components or in combinations with further active ingredients, have recently reached the market of the dietary supplements, health foods, energy foods and similar products.
It has long since been known that L(xe2x88x92)-carnitine and its alkanoyl derivatives are extremely hygroscopic and not very stable when they occur as inner sats (or xe2x80x9cbetainesxe2x80x9d) as represented by the formula. 
wherein Rxe2x95x90H or C1-C5 lower alkanoyl.
This leads to complex problems of processing, stability and storage both of the raw materials and of the finished products. For example, L(xe2x88x92)-carnitine tablets have to be packaged in blisters to keep them out of contact with the air, since, otherwise, even in the presence of normal humidity conditions, they would undergo alterations, swelling up and becoming pasty and sticky.
Since the salts of L(xe2x88x92)-carnitine and its alkanoyl derivatives known to-date present the same therapeutic, nutritional or dietetic activities, respectively, as the so-called inner salts (or xe2x80x9cbetainesxe2x80x9d), the problem of the hygroscopicity of the inner salts has tentatively been solved by salifying them with xe2x80x9cpharmacologically acceptablexe2x80x9d acids, which do not present unwanted toxic or side effects.
There is now an extensive body of literature, particularly patents, disclosing th e production of such stable, non-hygroscopic salts.
Among L-carnitine salts, particularly L-carnitine tartrate and L-carnitine acid fumarate have to-date found practical utilization.
Although the aforesaid xe2x80x9cpharmacologically acceptablexe2x80x9d salts solve the problem of the hygroscopicity of L-carnitine inner salt more or less satisfactorily, in none of the known salts the anion moiety co-operates to enhance the nutritional, energetic and/or therapeutical efficacy which can be attributed to the xe2x80x9ccarnitinexe2x80x9d moiety of the salts themselves.
Furthermore, none of the acids used for producing non-hygroscopic L-carnitine salts is capable of forming non-hygroscopic salts of alkanoyl L-carnitine. Thus, for example, whereas L(xe2x88x92)-carnitine acid fumarate and L(xe2x88x92)-carnitine tartrate are non-hygroscopic compounds, acetyl L(xe2x88x92)-carnitine acid fumarate and tartrate, respectively, are strongly hygroscopic compounds, which present the same drawbacks as the corresponding inner salt.
The object of the present invention is to provide stable, non-hygroscopic salts of L-carnitine and lower alkanoyl L-carnitine which possess an enhanced therapeutical and/or nutritional efficacy with respect to the corresponding inner salts.
L-carnitine and alkanoyl L-carnitine choline tartrates are reported to be stable and non-hygroscopic salts in WO 98/47857.
As regards L-carnitine salts with aminoacids, EP-A1-0 354 848 discloses pharmaceutical compositions comprising L-carnitine lysinate as active ingredient, whose preparation and physico-chemical characteristics, however, are not reported. In particular, this reference does not disclose whether the aforesaid L-carnitine lysinate is a hygroscopic or non-hygroscopic substance.
It is, therefore, apparent that the utility of the salts of the present invention is to be found not only in their lack of hygroscopicity and higher stability with respect to their corresponding inner salts, but also insofar as their anion moiety contributes to the nutritional, energetic and/or therapeutic efficacy of the salt as a whole. The aforesaid efficacy of these novel salts is, therefore; not to be attributed exclusively to the xe2x80x9ccarnitinexe2x80x9d moiety of the salt.
The aforesaid object is achieved by the salts of L-carnitine and alkanoyl L-carnitine with creatine and ornithine having the formula (I): 
wherein:
R is hydrogen or a straight or branched-chain alkanoyl group having 2-5 carbon atoms; and
Yxe2x88x92 is selected from: 
wherein A is a pharmacologically acceptable acid performing the function of salifying the amino group or groups. Preferably, A is a hydrohalogen acid, such as hydrochloric acid, or phosphoric acid.
When R is alkanoyl, it is preferably selected from the group comprising acetyl, propionyl, butyryl, valeryl and isovaleryl.
Creatine is an organic, nitrogen compound present in considerable amounts in the skeletal muscle tissue of vertebrates wherein about ⅔ thereof occurs as creatine phosphate.
Creatine is biosynthesized mainly in the liver and kidneys from three amino acids: glycine which provides the carbon skeleton, arginine which releases the amidino group and methionine which releases the methyl group. Creatine is excreted with urine as creatinine. Creatine, can be taken with the diet since it is principally present in meat. However, in order to take 10 grams/day of creatine, 2.5 kg of meat should be eaten. The exogenous supply and endogenous biosynthesis must compensate for the daily turn-over of creatine to creatinine which in a 70-kg male subject can be estimated at about two grams.
The physiologic role of creatine is extremely important: principally in the skeletal muscle, but in the brain, liver and kidneys as well, creatinexe2x80x94by reversibly taking up ATP""s phosphate groupsxe2x80x94plays the role of reservoir of the energy-rich phosphate radicals. This reaction is critically important since ATP can not be stored in tissues in excess of a very limited threshold. It is creatine phosphate whose content in tissues is five times as much that of ATP, which provides for phosphate groups supply. Following a moderately wearying physical exertion, the creatine phosphate present in the skeletal muscle decreases in a far relevant amount than ATP does, thus showing that creatine phosphate rephosphorilates ADP as ATP becomes dephospharilated.
When the rate of ATP""s metabolic production exceeds ATP""s utilization, this results in creatine phosphate formation. Creatine phosphate is, therefore, a reservoir of immediately available energy, suitable for counterbalancing energy demands exceeding ATP""s synthesis rate in metabolic phosphorylation processes.
Creatine is mainly taken by athletes and sportsmen insofar as it increases the skeletal musculature if its intake is accompanied by lasting physical exertion. Creatine intake results in a lowering of fat while it enhances skeletal muscle. Recent researches have shown that the combined intake of creatine and carbohydrates enhances creatine effects owing to insuline production that is stimulated by simple sugars which likely play a role in creatine exportation to muscle cells.
Ornithine, a non-proteogenic amino acid is a lower homolog of lysine and an important intermediate in urea biosynthesis cycle wherein it is synthesized by arginine transguanidinization. Ornithine can also be converted to glutamic acid.
It is, therefore, apparent the advantage of having at one""s disposal novel carnitine salts which, in addition of being stable and withstanding environments of high relative humidity (60-70%), combine the therapeutical, nutritional and energizing properties of both L-carnitine or its alkanoyl derivatives and creatine or ornithine.